This package aims to bring the joy of zustand to flutter. A huge shoutout to @dai-shi, the original author of zustand.

A small, fast and scalable bearbones state-management solution using simplified flux principles. Has a comfy API. Isn't boilerplatey or opinionated.

Don't disregard it because it's cute. It has quite the claws. Lot's of time was spent making the API flexible while keeping it simple and easy to use.

⚠️ This package is in its early stages and the API may change.

• Pub package
• Source code

First, wrap your app in a scope

Zustand uses scope to notify widgets to rebuild.

void main() {
  runApp(const StoreScope(child: MyApp()));
}

Next, create a store

Your store receives actions and emits state. State has to be updated immutably.

class BearStore extends Store<int> {
  BearStore() : super(0);

  void increasePopulation() => set(state + 1);
  void removeAllBears() => set(0);
}

BearStore useBearStore() => create(() => BearStore());

Then bind your widgets, and that's it!

Use the store anywhere. Call it or select from it to rebuild when it changes.

Widget build(BuildContext context) {
  final bears = useBearStore().select(context, (state) => state);
  return ElevatedButton(
    onPressed: useBearStore().increasePopulation,
    child: Text('Bears: $bears'),
  );
}

Why zustand over BloC?

• Simple and un-opinionated
• Less boilerplate
• Access stores without context
• Wrap your app once

Why zustand over riverpod?

• Doesn't require code generation
• Simple
• Less boilerplate

Why zustand over provider?

• Less boilerplate
• Centralized, action-based state management
• Context-free usage

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Recipes

Fetching everything

You can, but bear in mind that it will cause the component to update on every state change!

final bears = useBearStore().select(context, (state) => state);

Selecting multiple state slices

It detects changes with equality (old == new). This is efficient for atomic state picks.

Widget build(BuildContext context) {
  final nuts = useBearStore().select(context, (state) => state.nuts);
  final honey = useBearStore().select(context, (state) => state.honey);
}

Reacting to state changes

You can add listeners to any store using the StoreListener widget.

Widget build(BuildContext context) {
  return StoreListener(
    [
      useBearStore().listen(
        (context, state) {
          print("There are $state bears");
        },
        condition: (prev, next) => prev != next && next == 5,
      ),
    ],
    child: Container(...),
  );
}

Async actions

Just call set when you're ready, zustand doesn't care if your actions are async or not.

class BearStore extends Store<int> {
  BearStore() : super(0);

  Future<void> loadFishies() async {
    final fishies = await fetch(pond);
    set(fishies.length);
  }
}

Read from state in actions

Each store exposes a state property that you can access directly in your actions.

class BearStore extends Store<int> {
  BearStore() : super(0);

  void increasePopulation() {
    set(state + 1);
  }
}

Subscribe to store changes manually

If you want to watch state changes from outside of the build method, you can listen to changes to state directly.

void initState() {
  _sub = useBearStore().stream.listen((state) {
    print("Bears: $state");
  });
}

void dispose() {
  // don't forget to cancel
  _sub?.cancel(); 
}

Motivation

If you'd like to learn more about why this library exists, check out the motivation document.

Contributing

If you like the package and want to contribute, feel free to open and issue or create a PR. I'm always open to suggestions and improvements.

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keywords: flutter, state management, zustand, bear, cute, simple, fast, scalable, flux, store, action, state, provider, riverpod, bloc